The present invention relates to a manufacturing managing method.
Conventionally, in a case that semiconductor wafers or other devices are manufactured regularly or by way of experimental trial, a wafer loading carrier (or a cassette, or a casing, which are collectively referred to as a carrier) conveys a plurality of (e.g. 25) wafers serving as workpieces. In the following description, respective wafers are explained as a representative example of the workpiece. For example, as shown in FIG. 18, the group of wafers belonging to the same manufacturing lot, i.e. passing the same manufacturing process flow, is loaded on the same carrier. Such a managing method and a related control or assist system are conventionally employed in the manufacturing facility of the semiconductor wafers.
Hereinafter, the manufacturing process flow will be explained. In general, the manufacturing processes include work steps or stages that beforehand determine or specify various conditions with respect to processing or machining, measurement, inspection, etc. In this case, various conditions include exposure reticles or exposure masks used in the photolithographic process as well as patterning programs for the laser beam irradiation.
Furthermore, each manufacturing lot constitutes a group of wafers that are identical with each other in a manufacturing start line or other base point. In other words, the manufacturing lot is a group of wafers that are basically the same in the manufacturing process flow. An advantage of using this manufacturing method is easiness in management because the carrier and the manufacturing lot are basically in a one-to-one relationship or in an n-to-1 relationship.
However, according to this method, especially in a factory having a multi-kind and small quantity type product configuration, manufacturing the required products at required timing necessarily decreases the wafer loading number (or rate) of each carrier. The in-process efficiency in each manufacturing, processing or machining (or, measuring or inspecting) apparatus decreases accordingly. Furthermore, this prevents the effective use of the carrier and accordingly worsens the space saving and undesirably increases the frequency in conveyance (transportation).
Increasing the wafer loading number (or rate) of the carrier to improve the in-process efficiency will result in increase of the front-loading manufacturing work to an extent exceeding a required amount. Furthermore, a great number of unnecessary wafers will remain in respective processes of the entire manufacturing flow. This leads to increase in inventory or generation of hoarded products. As a result, this disturbs an earlier delivery of manufactured products.
Furthermore, even in a factory having a large quantity type product configuration, loading a plurality of (e.g. 25) wafers on a carrier will be subjected to predestinated check or various measurements and inspections on processed or machined semi-finished products in the way of manufacturing processes to remove defective products. In such a case, defining the relationship between the carrier and the manufacturing lot to be basically one-to-one or n-to-1 will decrease the wafer loading number (or rate) of the carrier.
Similarly, in the way of manufacturing processes, separating the carriers according to the quality level (i.e. rank) to realize classification of the wafers according to the quality level (i.e. rank) will decrease the wafer loading number (or rate). Alternatively, successively loading the wafers sorted according to the quality level (rank) on a carrier without changing the manufacturing lot will make the relationship between the carrier and the manufacturing lot vague and accordingly will make it difficult to manage the relationship between the carrier and the manufacturing lot.
To solve the above problems, for example, the Japanese Patent Application Laid-open No. 5-109596 discloses a manufacturing and controlling method including a lot division step of dividing the lot into some groups each consisting of wafers having the same processing conditions, a step of displaying manufacturing processing conditions of respective divided lot groups, and a step of reuniting the divided lot groups after finishing the processes differentiated in manufacturing processing conditions. Using such a method is not preferable in that the lot number does not agree with the manufacturing process flow (i.e. historical data).
Furthermore, it may be possible to add facilities to enhance the manufacturing capability or capacity for each manufacturing, processing or machining (or, measuring or inspecting) apparatus. However, this method apparently retrogrades with respect to efficient use (or operation) of respective apparatuses as well as efficient investment (or supply).
From the above-described background, especially in a factory having a multi-kind and small quantity type product configuration, the wafer-based management system has been generally considered as being prospective especially for the manufacturing method and its control and a related managing system. In this case, each manufacturing lot is managed based on the wafer (i.e. wafer sheet-feed based management). For example, ID assigned wafers are grouped into the same lot. The wafer loading carrier is used to load a plurality of (e.g. 25) wafers. The management is complicated and the system is complicated too. Thus, this is practically not used as an effect manufacturing method and its control managing or assisting system.
Furthermore, improving an existing system using one-to-one relationship in managing the carrier and the manufacturing lot will generally require a large-scale replacement of the system. Depending on stepwise efficient investment (supply) while utilizing the existing properties (including continuous manufacturing activities in the existing factories) could not be practically realized.
Although the above-described explanation is based on an example of the factory having the multi-kind and small quantity type product configuration, the explanation will be equally applied to a case where the number of wafers on each carrier is smaller because of recent increase in the aperture size of wafers (e.g. 300 mm) and accordingly because of substantial increase in the chip number manufactured from one piece of wafer.